1. Field of the Invention
The invention relates in general to a polysiloxane, and more particularly to a polysiloxane containing tertiary amine groups and having a comb-like structure for using as an anti-yellowing fiber treating agent.
2. Description of the Related Art
Organic polysiloxane is characterized by low surface tension, lubricating, softening and releasing properties. Therefore, it is usually utilized to modify the surface properties of other polymers. However before using, certain organic functional groups are firstly introduced to the polysiloxane so that the hydrophilic or hydrophobic property of the polysiloxane is adjusted, and some functional groups in the polysiloxane may react with the modified polymers to form permanent bonds. The categories and the amount, as well as the locations of the functional groups in the polysiloxane will influence not only the properties of the polysiloxane itself but also the properties of the modified polymers.
Reactive hydrophilic amine groups are one of the commonest functional groups introduced to polysiloxane. Polysiloxane with such amine groups is usually applied to modify resins, or used as additive for paint and ink, or as post-treating agent for fibers.
When applied in paint, polysiloxane with amine groups improves the paint with luster and surface protection, and improves the durability of the paint. It is usually formulated in metal paint and floor paint as disclosed in U.S. Pat. Nos. 3,856,733, 3,960,575, 4,247,330, 4,070,510, and 3,429,842.
When applied in fiber post-treatment, polysiloxane with amine groups improves the softness of the fibers. The friction between fibers results in slippery difficulty and thus actual uncomfort. If oily agent exists on the surface of the fibers, the friction therebetween can be reduced and the fabric becomes softer. However, the process of using polysiloxane as fiber treating agent has to be performed in water bath so that the amine groups can be introduced to the polysiloxane to increase its water solubility as disclosed in U.S. Pat. No. 4,725,635, Japan patent publication no. 56-45406, 54-131096 and 53-98499.
The polymerization processes provided by the above mentioned patents all use hydrolyzed silane and chain extenders, to polymerize. The polysiloxane thus formed usually has comb-like amine side chains with irregular intervals. Emulsifier has to be added or the amount of amine groups has to be increased to make the polymer uniformly dispersed. However, polysiloxane with higher amount of amine groups when used as fiber treating agent will cause yellowing. On the other hand, if the amount of the amine groups is limited to a certain degree, the molecular weight of the polysiloxane main chain is consequently limited, which will in turn limit the improvement of the softness of the fibers. The molecular weight of the hydrolyzed silane with amine groups will limit the molecular weight of the ring-opened polysiloxane.
The above-mentioned polysiloxane with amine groups is commercialized, for example, 531, 536 of Dow Corning corp., 784, 785 of SWS corp., and 2133, 2135 of GE corp.
FIG. 1 illustrates the molecular structure of a conventional polysiloxane with primary amine groups. The main chain of the polysiloxane determines the lubricating, releasing and softening properties. The side chains with amine groups determine the dispersibility and reactivity. Therefore, the application of the polysiloxane with amine groups is limited by the amount of the amine groups and the locations of the side chains.
The conventional preparation includes adding 100 g of .gamma.-3-propyldimethylaminodimethoxysilane into a reactor, and adding 7 g of water, keeping at a temperature between 60.about.80.degree. C. to proceed a hydrolysis reaction. Finally, a hydrolyzed prepolymer with primary amine groups, having a viscosity of 100.about.200 cps, is then obtained. Polysiloxane with primary amine groups, having a viscosity of about 800.about.1000 cps, can be obtained by firstly adding 16 g of the hydrolyzed prepolymer with primary amine groups and 184 g of octamethyltetracyclosiloxane into a reaction bottle and then adding 0.5 g of potassium hydroxide, stirring and heating up to 130.degree. C. for 3.about.4 hours.
This polysiloxane contains primary amine groups which have active hydrogen groups will result in fiber yellowing when it is applied in fiber processing.